Frag tank plumbing.

[WarDog]

You need to have one tank higher than the other. You would need to drill this higher tank so it can drain into the lower tank, preferably with a herbie or bean animal (but a durso will do the trick also). The return pump in the lower tank would then feed the higher tank. Only one pump.

A sump doesnt need to be below the display, just lower than it. My current build has the sump next to the display and approximately 12 inches lower.